The present invention relates to apparatus and methods for collecting debris so as to protect a well bore and its contents during well bore operations, such as perforating the well. Particularly, a junk basket is disclosed which is run into the well bore atop a bridge plug.
After casing is placed in a well bore, various operations can be performed. Workover operations, including perforation of the casing produce significant quantities of debris. It is usually desirable to isolate those portions of the well which are not being worked on. Where the unaffected zones are lower in the well bore, a bridge plug is run in and set in position below the intended work zone and above the zone to be protected. A junk basket is subsequently placed on, or above, the bridge plug to collect debris generated from the operation.
For instance, in the case where hydraulic fracturing of a formation is performed at an upper set of perforations in the casing, in a first trip, a retrievable bridge plug is set below the upper perforations to block the lower well bore. A setting tool is run in from the surface carrying the bridge plug. An insertion rod associated with the setting tool is attached to, and holds, the plug in position while an outer sleeve of the setting tool imparts a downward force, setting the sealing elements and slips. Then, a link is sheared to separate the insertion rod from the plug. In a second trip, a junk basket is lowered to sit atop the set bridge plug. The workover operation is performed. Frac balls or ball sealers are often used in fracturing so as to gravitate to and temporarily block some perforations for better distribution of fracturing fluid and proppant. Ball sealers must be later removed or they become a significant nuisance. After the workover, in a third trip, a cleanout tool is run into the hole, circulating fluid for washing light debris away from the top of the junk basket and carrying it uphole for removal at the surface. In a fourth trip, a retrieving tool is run in which includes a fish for attaching to the junk basket and fishing it out of the well.
The junk basket typically contains debris including particulate matter (sand) and ball sealers. As required for the particular instance, a fifth trip may be expended to retrieve the bridge plug.
In summary, without including additional trips resulting from experiencing problems, a least five trips are performed: run in and set the bridge plug; run in junk basket; cleanup well bore to junk basket, retrieve junk basket, retrieve the bridge plug.
Each run in operation and trip out costs time and correspondingly, money. Beside the number of trips, several difficulties are associated with the above-described conventional operation. As the diameter of a junk basket is necessarily close to that of the casing to which it is fitted, the sand from the workover tends to pack between the junk basket and the casing, binding and generally making it difficult to pull the basket during retrieval. Additional difficulties are associated with the means for retrieval. As stated, junk baskets fit closely within the well casing. It is known with conventional baskets to use a central and upward projection or fish-neck. To maximize basket capacity, the fish neck diameter is minimized. The retrieval tool must locate and connect to the fish-neck, however it must do so without laterally deflecting it and bending it, which jeopardizes chances of retrieval. Another problem with the conventional baskets is the lack of reliable feedback which enables the operator to ascertain when the fish has actually latched onto the junk basket. Baskets are light and are not normally detected. Many a trip out is performed to find nothing on the end of the retrieving tool, requiring one or more additional fishing trips.
For addressing both economics and reliability issues, there is a need for an improved junk-basket and means of installing and retrieving same.
A novel junk basket is provided and a method of operation, which in a preferred form, is attached to a bridge plug with shear pins and set simultaneously therewith, thus requiring only a basket/plug setting step, a basket retrieving step shearing the pins, and a plug retrieving step; not the five or more steps of the prior art. Further, the preferred basket maximizes debris capacity, makes fishing retrieval more reliable, latching of the basket is positively identified and the basket is more easily withdrawn from a cased well bore.
The preferred apparatus is a basket having a tubular sleeve with a substantially open bore therethrough, the sleeve fitting closely in the casing. The top end of the basket forms a robust internal latch and adjacent the top end are fluid slots to the casing. The basket has a bottom or floor which is movable in the bore but cannot escape the basket""s bottom end. In the well bore, the basket floor is supported by a protuberance such as the bridge plug thereby spacing the floor upwardly in the basket bore. Once filled with debris and latched with a retrieving tool, the junk basket is lifted upwardly from the protuberance causing loss of support for the floor and allowing it to fall to the bottom of the basket where its fall is arrested, but not before the volume within the basket is suddenly increased for the loosening of the collected debris in the basket and loosening of the packed debris between the sleeve and casing through the slots, and thereby aiding in recovery.
In a broad apparatus aspect then, a junk basket for collecting debris comprises:
a tubular sleeve which fits within a well bore, the sleeve having a bore extending axially therethrough and having top and bottom ends;
an internal retrieving latch formed at the top end of the sleeve;
a basket floor for substantially blocking the sleeve""s bore and being axially movable therein;
an internal shoulder formed within the sleeve""s bottom end for supporting the basket floor preventing its passage downwardly therethrough, the basket floor being operative between at least two positions being,
(1) a first collection position wherein basket floor is supported and spaced somewhat upwardly from the sleeve""s bottom end for forming a collection volume for collecting debris, and
(2) a second retrieving position wherein the basket floor falls to the internal shoulder when the junk basket is lifted by a retrieving device, thereby increasing the collection volume and whereby the collected debris is loosened within and outside the sleeve permitting ease of retrieving.
Preferably the basket floor is supported on a bridge plug anchored in the well bore. More preferably, the sleeve is attached to the bridge plug with shear pins so that, once the retrieving latch is engaged, then at predetermined weight of a retrieving string, the pins shear and the operator is clearly aware the basket was caught and will be retrieved.
More preferably, the basket floor is formed with an axial port so an insertion rod can be connected to the bridge plug through the floor, the basket thereby being capable of being run in with the bridge plug and does not interfere with the setting of the plug. Provision for axial slots through the sleeve permits fluid communication with the casing annulus which can aid in the retrieval process.
The above apparatus enables a novel method of setting and retrieving a bridge plug and junk basket simultaneously.
In a broad method aspect then, a downhole tool, such as a bridge plug is deployed simultaneously with a junk basket using a setting tool and insertion rod, the downhole tool having a top protuberance comprising the steps of:
connecting a junk basket to the top of the downhole tool, the junk basket having a tubular sleeve with top and bottom ends, an open bore extending axially through from the top end through to the bottom end, and having a basket floor which blocks the sleeve""s bore, the insertion rod passing through the sleeve""s bore and to an axial port in the basket floor, and a ball which is movable within the sleeve""s bore and is capable of blocking the axial port;
releasably connecting the insertion rod to a rod connection at the top protuberance through the sleeve""s bore;
inserting the insertion rod, junk basket and downhole tool into the well bore;
setting the downhole tool to anchor it within the well bore; and
releasing the insertion rod from the rod connection so that the junk basket remains in the well bore above the downhole tool and the ball is able to block the axial port.
Preferably, the sleeve has one or more fluid ports for communication between its bore and the well bore and basket floor is movable within the sleeve""s bore and initially spaced upwardly by the protuberance so that when the basket is retrieved, the ball is blocking the axial port and the floor drops, increasing the basket volume and loosening debris within and outside the basket. More preferably, the basket""s sleeve is attached to the downhole tool with shear pins for enabling confirmation of the latching of a retrieval tool and thus completing the method for deploying, collecting debris and retrieving the debris.